SEPTEMBER, 1906. Vol. XXXI., NO. 366. THE ANALYST. PROCEEDINGS OF THE SOCIETY OF PUBLIC ANALYSTS. ON THE EXAMINATION OF OLIVE, LINSEED, AND OTHER OILS. BY R. T. THOMSON AND H. DUNLOP. ( R e a d at the Ilrieetirtg, J u n e 14, 1906.) HAVING seen reason, after careful investigation, to adopt Wijs' method of determining the iodine value of oils in place of the Hiibl method, we have made an examination of various oils of undoubted genuineness, and propose in the present paper to describe the results. As we have stated before, there is an element of uncertainty and unreliability in the Hub1 method, and in any event the Wijs and Hiibl results cannot be depended on as being interchangeable. It is therefore of importance that a fresh series of iodine values by the Wijs method should be constructed, and this we have done for several oils in the present paper, and' embodied the results, along with those of other constants, in Tables I.and II., p. 282. In the case of the olive oils prepared from the olives by ourselves, those extracted by carbon bisulphide were from the residue left after pressing out the bulk of the oil, and it will be observed that there is little difference between the two varieties. It is evident from these results that a genuine olive oil may vary in iodine value from 81 to 89, and may be regarded as such if the other constants are normal. There is a peculiarity with regard to the Mogador oil, which has an extremely high iodine value, while the refractorneter reading is lower than would be expected. We have found with regard to linseed and fish-liver oils that the iodine value and refractometer reading practically rise and fall simultaneously, but olive oil appears t o be quite erratic in this respect, as will be seen by an inspection of the tables.This difference is no doubt partly due to the influence of the free fatty acids, which, it has been stated, lower the refractive power; and this is undoubtedly the case, as will be seen from Table III., p. 283.282 THE ANALYST. TABLE I . Oils extracted by ourselves from the Seed o r Fruit, so that their Genuineness can be absolutely depended upon. Olive oil (Spanish, green, Olive oil (Spanish, green, Olive oil (Spanish, ripe, Olive oil (Spanish, ripe, Olive oil (Turkish, very Linseed oil (Rigi'FJeed) ' * Linseed oil (St. Peters- Linseed oil ( N o r t h Linseed oil (Calcutta) ...Linseed oil (River Plate) Ravison oil . . . ... Jsmba, oil ..- Rape oil (East India) ... Almond oil ... ... Gas tor oil ... ... by pressure) ... ... by CS,) ... ... by pressure) . . . ... by CS,) ... ... ripe) ... burg) ... American) . . . ... Iodine Value (Wijs). 83.20 83-20 88.95 88.15 89.1 205.4 200.0 194.6 188.6 185.5 118.1 98.3 104.5 98-1 85.6 Zeiss Refracto- nieter a t 25" C. 61-2 61.2 61.3 62.2 61.2 85.5 84.2 83.2 81.7 81.0 71.0 67.2 68.0 64-3 78.3 Saponifi- cation Value. Per Cent. 19.56 19.21 19.28 19.14 19.21 19.21 19.28 19.21 19.28 19.14 18.13 17.53 17.53 18-16 - Unsa- ponifiaktle Matter. Per Cent. 1.25 1.62 1.34 1.52 1.24 1.25 1.23 1.10 0.88 1-25 1.65 1.02 1.02 0.60 - TABLE 11. Oils obtained from Reliable Sources.Olive oil (Crete) . . . ... ,, (Italian) ... ,, (Sicilian) ... ,, (Levant) ... ,, (Algerian) ... ,, (Spanish) ... ,, (Mogador) ... Sunflower oil (Russian) (by Hubl's method) , . . Arachis oil ... 3 ) (Syrian) ... Poppy-seed oil ... ... ... Iodine Value (Wijs). 81-2 83.5 84.1 84.4 85-1 85.3 86.6 94.3 140.0 131.3 87.5 Zeiss Refracto- meter a t 25" C. 60.2 59.7 60.0 61.0 60.7 60.1 61.2 60.5 71.0 70.0 62.6 Saponifi- cation Value. Per Cent. 19.14 19.21 19.07 19.21 19.14 19.14 19.21 19.07 19-28 18.93 19.14 Specific Gravity, 60" F. Free Acid. Per Cent. Unsa- ponifiable Matter. Per Cent. Specific Gravity, 60" F. 0.9155 0.9157 0-9144 0.9159 0.9150 0.9145 0.9161 0.9150 0.9243 0.9220 0.9164 Free Acid. Per Cent. 9.40 16.61 11.50 9.32 5.62 11.76 7.27 24.72 1-62 1.21 -THE ANALYST. 283 TABLE 111.Showing the E f e c t of Free F a t t y Acids on the Refractive Power of Olive Oil. ___ ._ _ _ ~ _ _ Iodine value before removal of free acid ... ... Iodine value after removal of free acid Zeiss refractometer, 25" C. before removal of free acid Zeiss refractometer, 25" C. after removal of free acid Free oleic acid, per cent. before removal of free acid Free oleic acid, per cent. after removal of free acid ... Olive Oil (Mogador). 94.30 93.45 60.50 63.40 24.72 0.32 Olive Oil (I talian). 83.50 80-45 59.70 61-00 16-61 0-27 TABLE IV. Comparison of Iodine Value and Refractive Power of Linseed and certniiz Fish- liver Oils. Linseed oil I ) S kat e-liver (Riga) ... ... ... ... ... (St. Petersburg) ... ... ... ... (North America) , .. ... ... ... Linseed oil (Calcutta) ... ... ... ... ... Linseed oil (River Plate). .. ... ... ... ... Whiting-liver oil ... ... ... ... ... ... oil ... ... ... ... ... ... Haddock-liver oil ... ... ..- ... ,.. .., Iodine Value. 205.4 200.0 194.6 191.1 188.6 186.4 185.5 184.2 Zeiss Refraciometer a t 25" C. 85.5 84.2 83.2 82.5 81.7 81.0 81.0 81.0 The differences referred to cannot, however, be entirely explained by the influence .of the free acid, as will be apparent from an examination of the results in Tables I. and II., and especially of those of the two oils extracted from the same Spanish ripe olives, where the oil with the lower iodine value shows the higher refractive power, the free acids being practically the same. The different samples of linseed from which we prepared the oils were carefully ,examined, and any foreign seeds removed, so that only the genuine linseed wa6 employed.I t will be observed that the iodine value for the oil extracted from the Riga seed is, we believe, the highest on record, while that from the River Plate has an iodine value much higher than what was recorded by one of us some years since. There can be no doubt, however, that these high figures are due partly to the use of the Wijs in place of the Hub1 method, and where the former is employed any iodine value below 180 should lead to a more searching examination of the oil. ,4s regards the other oils of which the constants are included in the tables, it is scarcely necessary to make any remarks, except that the jamba oil cannot be .distinguished from rape oil by ordinary means, and that in some few cases the284 THE ANALYST, employment of the refractometer along with the iodine value may be useful, although the former is of no independent importance. In conclusion, we would draw particular attention to the peculiar similarity between various linseed oils and certain fish-liver oils as regards iodine value and refractive power, as shown in Table IV., p. 283. Of course, linseed oils have a, distinctly higher specific gravity than the fish-liver oils, but the saponification value and unsaponifiable matter are much the same in each.